Cathode ray tube



CATHODE RAY TUBE Filed July 26, 1934 INVENTO'R MAX Azv LL jww ATTORNEY Patented Dec. 13, 1938 UNETED CATHODE RAY TUBE Max Knoll, Berlin, Germany,

assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, German Germany Application July 26, 1934, Serial No. 737

y, a corporation of In Germany July 31, 1933 2 Claims.

This invention relates to a cathode ray tube which can be used as receiver for purposes of television, and which has the advantage over the ages.

This invention is related to my co-pending applications 737,022, filed July 26, 1934, and entitled Cathode ray tube, and 737,024 filed July 26, 1934, and entitled Cathode ray tube.

To this end, and in accordance with the invention, a grid is to be placed in front of the cathode of the tube, possessing against the cathode a constant positive potential, and furthermore at a larger distance from the cathode a second grid is provided having negative potential as regards the first mentioned grid, the value of this potential varying in dependence upon the voltage serving for the modulation of the brightness of the luminescent spot.

Referring to the drawing in which embodiment of the invention is schematically illustrated, my invention will now be described in detail.

The cathode of the cathode ray tube is designated by ID, while II represents a disk galvanically connected thereto. At a small distance from the cathode a grid I2 is disposed charged, for instance, by a potential +100 volts against the cathode, and below the said grid a further grid 4 3 is placed having a negative potential against the first mentioned grid, whereby the latter potential changes depending upon the modulation of the brightness of the luminescent spot. Below grid I3 a third grid I4 is provided to which may be applied a positive potential of 2000 volts against the cathode. Grid I 4 represents the anode of the cathode ray tube. In place of grid I 4, an anode shutter may likewise be used having but a single opening.

The functioning of the arrangement is such, that the cathode rays are accelerated by the grid I2, While in the space between grid I2 and grid I 3 a decrease of the velocity occurs. The quantity d I3 depends of electrons passing through gri upon the respective potential difference between grid I3 and grid I2. As tests have shown, the arrangement according to the invention affords obtaining a variation of the luminosity of the luminous spot on the screen of the tube, within Wide limits, with considerably lower modulation voltages at grid l3, than was possible in the hitherto known arrangements. The grid I2 can be considered a virtual source of electrons from which electrons are already emitted at finite l0 velocity.

Having thus describe claim is:

1. In a cathode ray tube the combination of a thermionic emitter, a plane electrostatic guard electrode connected thereto and lying in the same plane as the emitting surface of the emitter, an accelerating electrode positioned parallel to and co-axial to the guard electrode and adapted to be maintained at positive potential relative to said cathode, a second accelerating electrode adapted to be maintained at a positive potential with respect to the first said accelerating electrode, and a modulating electrode extending parallel to and co-axial to the first and second accelerating electrodes and positioned intermediate said accelerating electrodes.

2. In a cathode ray tube the combination of a thermionic emitter, a plane electrostatic guard electrode connected thereto and lying in the same plane as the emitting surface of the emitter, a plane perforated accelerating electrode positioned parallel and co-axial to said guard electrode and adapted to be maintained at a positive potential relative to said cathode, a second perforated accelerating electrode positioned in spaced relationship with respect to said first electrode and adapted to be maintained at a positive potential with respect to said first accelerating electrode, and a modulating electrode extending parallel to and co-axial with said accelerating electrodes and located intermediate said accelerating electrodes.

d the invention, what I MAX KNOLL. 

